1. Technical Field
The present invention relates to a head unit including a nozzle group that discharges liquid, a liquid droplet discharging apparatus, a method for discharging liquid, and methods for manufacturing a color filter, an organic EL element and a wiring substrate.
2. Related Art
There are known a head unit with a nozzle group that discharges liquid and a liquid droplet discharging apparatus, in which a plurality of functional liquid discharging head units are intensively arranged such that the length of an array of the discharging heads in a main scanning direction is minimized (JP-A-2005-238821). In this case, main scanning means to discharge a functional liquid (liquid) during a relative movement between the functional liquid droplet discharging heads and an object on which droplets are discharged, and the main scanning direction means a direction of the relative movement therebetween.
In the above head unit, the functional liquid droplet discharging heads are juxtaposed so as to be displaced in the main scanning direction and in a sub scanning direction perpendicular therewith. Additionally, when viewed from the main scanning direction, nozzle sequences as nozzle groups, each including a plurality of nozzles discharging functional liquid droplets, are continuous with one another.
In the discharging head having the nozzle sequences, the amount of liquid discharged varies among the nozzles. In order to reduce the variation, there is known an inkjet recording apparatus that can equalize the discharging amount among the nozzles by driving discharging heads with nozzle sequences divided into a plurality of groups (JP-A-2002-196127).
JP-A-2005-238821 is a first example of related art.
JP-A-2002-196127 is a second example of related art.
FIGS. 18A and 18B each show a relationship between the arrangement of discharging heads and the discharging amount in a known method for discharging liquid. FIG. 18A shows the discharging amount varying among the discharging heads and FIG. 18B shows the discharging amount varying within the nozzle sequences of the discharging heads. More specifically, the drawings show the amounts of liquid discharged on the same drawing region in accordance with a drawing width of each of the discharging heads 1, 2 during a period of time in which a workpiece is moved relatively with the discharging heads 1, 2 four times in the main scanning direction. Regarding each of the discharging heads 1, 2, the nozzle sequences are divided into four groups and the discharging amounts of each group are temporarily digitized.
As shown in FIG. 18A, for example, in the head unit of the first example of related art, when the discharging amount varies between the discharging heads 1 and 2, there occurs a difference between the discharging amounts depending on the arrangement of the discharging heads 1 and 2 (in FIG. 18A, the discharging amount of the heads is 4.04 versus 4.16).
Additionally, as shown in FIG. 18B, for example, when there is an inclination in the distribution of the discharging amount of each group of nozzle sequences (in FIG. 18, the discharging amount varies from 1.01 to 1.04), a nozzle sequence group of one of the heads 1 and 2 discharges a maximum amount at a boundary between the discharging heads 1 and 2, whereas a nozzle sequence group of the other head discharges a minimum amount. Consequently, as compared to the case shown in FIG. 18A, liquid is discharged more unevenly.
The above variation of the discharging amounts across the discharging heads 1 and 2 results in noticeable uneven discharging distribution, particularly, at both ends of the nozzle sequences.
If the nozzle sequences are divided into a plurality of groups to drive the discharging heads to ward against the above defect, the driving mechanism becomes more complicated as the number of the discharging heads increases.